Punch travel detection arrangement



March 4, 1969 w. H. MCMONAGLE 3,

PUNCH TRAVEL DETECTION ARRANGE ENT Filed April 17, 1967 SCHMITT TRJGGER INVENTOR WILL/AM H. M MONAGLE gx a fw ATTORNEY United States Patent 3,430,529 PUNCH TRAVEL DETECTION ARRANGEMENT William H. McMonagle, Ambler, Pa., assignor to Sperry Rand Corporation, New York, N.Y., a corporation of Delaware Filed Apr. 17, 1967, Ser. No. 631, 485

US. Cl. 83-522 Int. Cl. B26d 7/28; G061: 1/04, 1/14 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to web material punching mechanisms and in particular to a device for verifying that the web material has actually been punctured.

Background In the prior art related to punching cards or tapes or Web material the mechanical linkage to the punch device was quite rugged and there was very little demand for high speed punching operations (when considered in terms of the punching art today). Accordingly there was very little concern given to whether or not a punch had traveled sufficiently into the die to puncture the web material. In this early art there were occasions when a punch failed to punch the card and on other occasions the punch tore the card in the punching operation, but these occasions were usually related to an electrical failure in the first instance and usually a worn punch or a worn die in the second instance. 7

As the demand for higher and higher punching speeds has come into being, the punching mechanisms have become designed with spring support actions and spring return actions so that very often there are flutter conditions created or the mechanism is not able to make a full mechanical excursion in the time allotted to do so by the electronics system. In addition there have been failures because of processor driver errors and interface errors. Accordingly there have been some attempts to verify whether or not a punch has actually pierced or punctured the card or web material, in response to an input signal, for instance, from a keyboard.

These attempts have included some optical schemes whereby when some linkage or the punch itself has been raised by an interposer above a certain physical level, a signal would be generated indicating that the web material had been punctured. In another effort, microswitches have been assigned to each punching position and as the punch is raised to a predetermined level the microswitch is closed thereby generating a signal indicating that the punch has traveled through that material. In each of the foregoing efforts and the other efforts, it has been found that the mechanism is bulky to install and very difiicult to service. For instance, in the case of the microswitches, the switches become misaligned after repeated closing and it is most difficult to perform a simple adjustment thereon. In addition the microswitches must include a large tolerance mechanically speaking because of the nature of the switch itself. Accordingly, the present invention provides a means to verify that the punch has traveled a sufficient distance to puncture the web material which means it is relatively simple to install, relatively service-free, and be- 3,430,529 Patented Mar. 4, 1969 cause of its nature it is very sensitive to the punch movement and can be operated within minimum tolerances.

Sumrrrary The present invention provides a linear differential transformer for each punch location. The core of the transformer is movable and is connected through a linkage to a lever arm which is connected to an associated punch. When the level arm, and therefore the punch, are at rest, the movable core is in an electrical or flux equilibrium position and therefore there is no output signal from the transformer. However, when the punch is moved upward by the interposer, in its travel to pass through the webbing material, the core is relocated and due to increased coupling the amplitude of the output signal is increased. A threshold device is connected to the output of the transformer and is arranged, depending upon the travel of the punch, such that when the signal exceeds a certain threshold it is indicative of the fact that the punch has traveled through the card or the web material.

The present invention can be better understood from the following description in conjunction with the drawings wherein:

FIGURE 1 shows the punch mechanism connected to a lever arm with the linkage being at rest;

FIGURE 2 shows the mechanism of FIGURE 1 with the punch and the linkage having been raised in a vertical direction; and

FIGURE 3 is a schematic diagram of the circuitry which is necessary to create a signal to indicate that the punch has traveled through the card.

Consider FIGURE 1 wherein there is shown a punch 11 movably connected to a lever arm 13. The punch 11 is connected to the lever arm 13 by virtue of the aperture 15 in the lever arm being threaded by the pin 17 of the punch. In the embodiment shown the punch in hollowed and the lever arm is fitted into the hollow portion with the pin passing therethrough. Obviously other arrangements of this movable connection could be effected. For instance, the pin 17 could actually be located on the side of the punch 11 and the aperture 15 of the lever arm would simply be passed over the pin. In another embodiment the pin 17 is L-shaped on the front of the punch 11 and the lever arm 13 has its aperture once again passed over the pin.

As can be seen in FIGURE 2 there is connected to the lever arms a pedestal member 19. The pedestal member is movably connected to the stem 21 of the movable core 23. The stem 21 is movably connected to the pedestal member 19 in a fashion which is similar to that just described with respect to the lever arm 13 being connected to the punch 11. In other words, the pedestal 19 has a pin over which an aperture in the stem 21 is placed.

In FIGURE 1 the movable core 23 is disposed in equilibrium between the primary winding 25 and the secondary winding 27. In FIGURE 1 the secondary winding 27 is schematically shown as a single winding and in some embodiments this is possible. However, in the preferred embodiment as can be seen in FIGURE 3 the secondary winding is actually made up of two separate windings 27a and 27b.

Further in FIGURE 1 it can be seen that the lever arm 13 is connected by means of a fiexure spring 29 to a solid portion of the machine depicted by the wall 31. Actually the fiexure spring is connected to some immovable portion of the machine so that there can be a pivot point developed for the lever arm in its movement upward.

FIGURE 2 shows the punch 11 having been driven upward through the webbing material or card. In FIG- URE 2 the punch has traveled the distance d. Because the aperture 15 is oversized with respect to the pin 17 the lever arm is permitted to make an arcuate movement as punch 11 is driven vertically. Accordingly, the pin of the pedestal member 19 moves the distance 1 as shown in FIGURE 2 and such movement in turn drives the movable core 23 a distance f between the primary winding and the secondary winding. As will be better appreciated from a description of FIGURE 3, when the movable core 23 is driven a distance 1 the flux coupling is no longer in equilibrium and a signal will be generated which is proportional to the distance moved. It should be further noted in FIGURE 2 that the spring 29 has been bent providing the pivot point for the lever arm 13.

In FIGURE 3 there is shown a schematic of the circuitry necessary to generate the signal. In FIGURE 3 the movable core 23 is shown located in an equilibrium position. When the movable core 23 is in a position shown in FIG- URE 3, and FIGURE 1, the voltage developed or induced in the secondary windings 27a-and 27b is equal and therefore there is no bias developed between the base and the emitter of the transistor 35. In FIGURE 3 the input is from the AC. generator 33.

When the movable core 23 of the transformer 24 is moved upward in FIGURE 3, which is analogous to moving it to the right in FIGURES 1 and 2, there is a greater voltage developed in the secondary winding 27a because of the improved flux coupling and simultaneously there is less voltage developed, because of the poorer coupling, in the secondary winding 27b. This differential in voltage appears as a forward bias across the base-to-emitter junction of the transistor 35 and causes that transistor to conduct.

The induced voltage in the secondary is of an AC. nature and hence there is an AC. signal developed at the collector of the transistor 35. The AC. signal at the collector of the transistor 35 is transmitted to the integrator circuit 37 whereat there is an envelope signal developed or a DC. signal developed. The SC. signal 38 is transmitted to the Schmitt trigger 39. If the DC signal 38 exceeds the threshold level which is necessary to cause the Schmitt trigger to conduct, then there will be a square wave signal 41 transmitted from the Schmitt trigger 39 for as long a period of time as the DC. signal 38 remains above the threshold level.

Now if for some reason the punch does not have the full travel which is necessary to puncture the web material, then the movement of the core 23 will not be suflicient to ultimately generate a DC. signal 38 that is above the threshold necessary to cause the Schmitt trigger 39 to conduct. Accordingly, there will be no output such as a pulse signal 41 and the system will not detect that a punchthrough has been eflFected. It should be understood that this signal 41 in addition to indicating that the punch has traveled into the card, is also used to be compared against an input signal generated by the keyboard (or whatever other input signal might be used) and hence there is a vertification of the electrical and mechanical operation against the input.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A punch travel detection device in a web punching mechanism comprising in combination: a punch member capable of moving vertically; a support member movably secured at one end thereof to said punch member and secured for rotation movement to a secure portion of said punching mechanism at said other end thereof; a differential transformer having a primary winding, a pair of secondary windings, and a movable core disposed to be moved between said primary winding and said secondary winding; signal source means connected to said primary winding to apply a signal thereto; and means movably connecting said movable core to said support member to move said core to ditferent positions between said primary and said windings to create a difference signal in said secondary windings which is commensurate with the movement of said punch member.

2. A punch travel detecting device according to claim 1 wherein there is further included circuitry means to detect when said difference signal has exceeded a predetermined threshold.

3. A punch travel detecting device according to claim 2 wherein said circuitry means includes an amplifier, an integrator circuit connected to the output of said amplifier; and a Schmitt trigger connected to the output of said integrated circuit to provide an output pulse in response to said difference signal exceeding said predetermined threshold.

References Cited Stanton et al.: IBM Technical Disclosure Bulletin, vol. 3, No. 3, August 1960, p. 35.

JAMES M. MEISTER, Primary Examiner.

U.S. Cl. X.R. 234-33 

